Protective equipment



Nov. 15, 1949 A. R. BROWN PROTECTIVE EQUIPMENT Filed Oct. 15, 1945 Patented Nov. 15, 1949 HNl-TED STATES PATENT OFFICE- PROTECTIVE EQUIPMENT.

Allan .R. Brown, El'mhurst,1ll.; assignor-to General "Electric X-Ray Corporation,. Chicago; Ill., a'corporation of New York Application October 15, 1945,'Serial No.-622,457

The present invention relates in general to electronicsend. has more particular reference to.-the-.operation. and control of X-ray generators.-

An Xeray generator, as-is well known, functions as a.-result .ofelectron impingement upon a suitable target,nelectrons being, emitted at the cathode of the-generator and directed therefrom upon the target, whichcomprises the anode of the generaton. Impingement of electrons on the anode is caused by the application of electrical potential-.-.between-:the-electron .emitting cathode and the-anode Current, also, is caused to flow between the-anode and cathode as a result of the travel of electrons from the-cathode to the target. Electrical-power for theoperation of the generatonis ordinarily supplied througha power. circuit,. connected withthe anode and cathode of thegenerator and includingthe secondary winding of a transformer.

Operation of the generator maybe controlled byvarying the electron emissivity of the cathode or; by varying the potential applied between the anode. and .cathode; or by varying both cathode excitation and anode-cathode potential.

Forzany selected value of cathode'excitation andz. anode-cathode; potential, at corresponding currentflow will occur in the anode-cathode circuitpcurrent flow-being measurable asafunction of. anode-cathode :potential, and increasing. with potential, and; vice-versa.. It .is,.of.course, desirable,u,if: not :essential, to providemeans ree sponsive. to overload: conditions and operable either to indicatesuch conditionsorto disable or otherwise perform protective functions with respect toythe .X-ray generating: equipment."- To this-end, suitable indicating-or control-apparatus mayzbe provided tooperate in response to overload; conditions represented by excessively high current flow-in theanode-cathode circuit. Since,

however; the generator, when operating at full loadpnormally'requires arelatively heavy cur-- rent'fi'ow, of th'eorderoftwo or more times the currentflowiencountered when thegenerator is in. operation under no load or small load condi tions,: it is :obvious that a currentresponsi-ve device adjusted toaccommodate the relatively heavy full load current flow may fail to operate underoverload conditions occurring when the generator:

is-inoperation under light :load.

erating system-when in. operation .under any load conditions within the range: of theequipment concerned; afurther. object being to. provide current. responsive control apparatus in which the. current. response. of the apparatus. varies as a function of the potential prevailing in the circuitwith which the apparatus is associated.

Another important object is .to provide. control means of the character mentioned. embodying a. saturable core transformer, and to. utilize the transformer for'the performance of an indicating or control function, in response to over-current conditions in a circuit with which the transformer is associated; afurthen object .being tovary the magnetic saturation. of the transformer as a function of the prevailing circuitload sothat thedevice may have substantially thesame response fonall .load values from zero to full load.

Anotherimportant object is. to utilize a satur-.- able transformer-for the purpose of monitoring a power circuit such as that employed in. energizing an X-ray generator, and to vary the saturation of the .transformer'as a-function .of the load of said. circuit, whereby to. actuate an operable control-device, suchas anassociatedrelay, in response to over-current conditions in saidcircuit.

The foregoing and numerous :other important objects, advantages, and. inherent functions of the invention wiilbecomeapparentasthe in-. vention' ismore fully understood from the followingdescription, which,.,taken in conjunction withthe accompanying drawings, discloses a preferred embodiment of the invention.

Referring to the drawing:

Thesingle figure is .a diagrammatic representa-. tion .of an Xeray. generator and associated .control equipment embodying-the:present invention;.

To illustrate the invention, the drawing shows an X-ray generator I having a. cathode 2 and an'anode3,. the;generator being of the type designed for operation at 'high :voltagesof theorder of .onemillionivolts, andmore; applied between the anode and cathode. Power for-energizing the generator is :supplied'through..a..transformer 4 having axprimary: winding 5 andarsecondary winding 6. The secondary windingincludes a portion 1 which is connected withthe cathode of the generator, through an adjustable current flow controldevice' 8, whereby to energize the cathode to render the same electron emissive.

The secondary winding .of the. transformer also end, the anode;3 may; begrounded through a.

suitable resistor ID. The high voltage end of the winding 9 may be connected with the cathode while its low voltage end may be connected to ground, through one or other of the sensitive microammeters H, by means of relay switches 12, in order to complete the anode-cathode circuit of the generator.

Specifically, the high voltage circuit extends from the cathode of the generator through the transformer winding 9 thence through a filter I3 adapted to by-pass the alternating current component directly to ground while delivering the direct current component to a normally closed switch M. The switch M may, of course, be a normally open switch adapted to be held closed so long as its operating solenoid ['5 is energized. As shown, however, the switch M is a normally closed switch which is operatively associated with and closable by a solenoid [5 when energized.

From the switch It the circuit extends to a pair of relay switches It. The switches iii are interlocked so that one is open when the other is closed, and vice-versa, one switch being normally open and the other normally closed, and both being operatively associated with a solenoid l1. One of the switches I6 is connected, through one of the meters II and preferably through a suitable ground connection and the resistor 10, to the anode 9 of the generator; and the other switch It is likewise connected, through the other meter ll, to the anode of the generator.

Power is delivered to the primary winding 5 of the transformer 4, through suitable supply and control circuit means 20, from an alternating current generator 2|. This alternator 2| has a field winding 22 energized through suitable circuits 23. The field energizing circuits 23 are controlled by relay switches 24 operable by an associated actuating solenoid 25. The switches 24 are preferably normally open switches and the solenoid 25 may be connected to a source of energizing power 26, in order to maintain the coil energized and the switches 24 closed, where-.- by to energize the field winding 22 of the alternator 2|, thereby causing it to supply power to the primary transformer winding 5, through the power circuit conductors 21, an adjustable choke 28 being included in the circuit for the purpose of providing unity power factor operation of the alternator. A condenser 34 also may be connected across the power circuit to introduce desired reactive characteristics.

In the event of an overload in the anode-cathode circuit of the generator, the control means may operate to short circuit the solenoid thereby allowing the switches 24 to open, thus reducing or cutting off the power supplied by the alternator to the primary winding of the transformer.

Alternately, the switches 24 may be normally closed and the protective system may be connected to energize the solenoid 25 to open them, or the system may be utilized to accomplish any other desired control function.

To this end, the protective system 29 preferably comprises a saturable core transformer 38 having a pair of lateral legs 29 and a central or common leg. The transformer has a pair of current windings 29' inductively coupled with the legs 29 and electrically connectedin the circuit 27 between the alternator 2 l and the primary winding 5 of the transformer 4. The saturable core transformer also includes a saturating coil 32- inductively coupled with the common leg of the transformer, which common leg has a part forming a magnetic loop or circuit with one of the legs 29, and another part forming a separate magnetic circuit with the other leg 29. This saturating coil 32 is connected in parallel relationship with respect to an adjustable resistor 33, said saturating coil and resistor being interposed in series relationship in the conductor 19 between the meters II and ground, whereby the saturation of the transformer is a proportional function of the direct current component of energy in the anode-cathode circuit of the X-ray generator I. The resistor 33, of course, is provided for adjusting the degree of saturation of the transformer 30.

Inductively coupled with each leg 29 of the transformer so is a coil 3|, the two coils 3| being connected in series with each other and with the actuating coil 36 of a preferably normally open relay switch 35 which, as shown, may be connected across the actuating coil 25 of the switch 24.

Under normal operating conditions, the current flow in the windings 29' of the saturable transformer Eli will develop insuificient current in the windings 3| to energize the winding 36 sufficiently to close the normally open switch 35. Consequently, the alternator 2i will function to energize the primary winding of the transformer t. In the event that an overload condition should develop, the increased current flow in the windings 29' will actuate the switch 35 through the coil 35 and the windings 3| of the saturable transformer. Since the saturation of the transformer as is accomplished as a function of the current flowing in the secondary winding of the power transformer l,'the response of the switch 35 can be made dependent upon the energy delivered in the anode-cathode circuit of the X- ray generator; hence the response of the control will be a function of the secondary load of the transformer 4. If said transformer 4 be lightly loaded, the current flow in the windings 29 will likewise be light, but the control system will function to close the switch 35 in response to any excess current flow in the windings 29'. At full load, a corresponding relatively large current will flow in the windings 29' without, however, causing the switch 35 to close,'the same being accomplished by the change in saturation of the transformer 33 due to the application of full load conditions in the winding 32. Any increase in current in the windings 29 above normal full load current, however, will cause closure of the switch 35 and thereby accomplish the protective function of the device.

The utilization of the anode-cathode curren of the X-ray-generator for the purpose of saturating the core of the transformer 30 will result in keeping the voltage applied across the coil 36 substantially constant throughout the operating range of the device from zero to maximum anodecathode current in the X-ray generator at full voltage. When properly adjusted, the relay 35 will not operate so long as the current in the primary transformer circuit 2'! is normal, within the. operating range of'the X-ray generator, but the relay will operate to disable or reduce the energy output of the alternator 2| whenever overload conditions are encountered.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the 5 invention, or sacrificing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

1. A control system for an X-ray generator having a cathode and a grounded anode, comprising an alternator having a field winding, circuit means for applying, between said anode and cathode, electrical energy delivered from said alternator, including a voltage step-up power transformer having a high voltage secondary winding connected with said cathode, and a primary winding, a saturable core relay transformer having a pair of circuit forming legs, each forming a portion of a separate magnetic circuit, and a common leg included in both of said magnetic circuits, a pair of power coils, each inductively coupled with a corresponding one of said circuit forming legs, said power coils being interconnected in series with said primary winding and said alternator, to form said circuit means, a saturating winding inductively coupled with said common leg, filter means to connect said secondary winding of the power transformer to ground through said saturating winding, whereby to energize the same in proportion to the uni-directional component of electrical current delivered between said anode and cathode, a pair of actuating windings inductively coupled, one with each of said magnetic circuits, and means controlled by current flow in said actuating windings, for variably energizing said field winding of the alternator.

2. A control system for an X-ray generator having an anode and a cathode, comprising an alternator having a field winding, circuit means for applying, between said anode and cathode, alternating current electrical power delivered from said alternator, including a voltage step-up power transformer having a high voltage secondary winding interconnected with said anode and cathode, and a primary winding, a saturable core relay transformer having a pair of circuit forming legs, each forming a portion of a separate magnetic circuit, and a common leg included in both of said magnetic circuits, a pair of power coils, each inductively coupled with a corresponding one of said circuit forming legs, said power coils being interconnected in series with said secondary winding and said alternator in said circuit means, a saturating winding inductively coupled with said common leg, means connected with the high voltage secondary winding of said power transformer and with said saturating winding for applying uni-directional energizing current in said saturating winding in proportion to the unidirectional component of electrical current delivered between said anode and cathode, a pair of actuating windings inductively coupled, one with each of said magnetic circuits of the relay transformer, and means controlled by current flow in said actuating windings for variably energizing said field winding of the alternator.

ALLAN R. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,943,464 Von Ohlsen et al. Jan. 16, 1934 2,066,919 West Jan. 5, 1937 2,140,349 Dawson Dec. 13, 1938 2,230,558 Bowen Feb. 4, 1941 2,319,378 Weisglass May 18, 1943 2,373,383 Christopher Apr. 10, 1945 

